This invention relates to a system for forming the joints of concrete slabs used in the construction of roadways, floors and the like. The basic system of forms, including screed and screed stakes, is well known and is illustrated, for example, in the Artigalas, et al. U.S. Pat. No. 3,057,269, dated Oct. 9, 1962, the Tone, et al. U.S. Pat. No. 3,357,324, dated Dec. 12, 1967, the Self U.S. Pat. No. 3,561,721, dated Feb. 9, 1981, the Tone U.S. Pat. No. 3,401,612, dated Sept. 17, 1968, the Welsh U.S. Pat. No. 3,497,172, dated Feb. 24, 1970, and the Berry U.S. Pat. No. 4,012,159, dated Mar. 15, 1977.
The screed stakes are generally made of metal, approximately 0.06 to 0.08 inches in thickness, approximately 1.00 to 1.25 inches in width and from 12 to 24 inches in length, depending upon the type of earth in which they are to be supported. Such stakes generally have a flat top and a pointed bottom to facilitate driving into the ground, as well as a longitudinal reinforcing bead or channel running from the pointed bottom to a point adjacent to the flat top. The flat top also facilitates insertion into a downwardly opening pocket formed on the top edge of the sheet metal screed with which the stakes are used. Such stakes may also be provided with upwardly opening pocket into which the lower edge of the screed may be inserted. In practice, this pocket often takes the form of one or more "fingers" formed out of the stake metal and extending upwardly alongside the stake.
The vertical depth of the concrete slabs being poured, and thus the vertical width of the screed necessary to form the key joint in the slab, differs substantially with the four typical dimensions being 3.5, 4.5, 5.5 and 7.5 inches. With generally known systems, it has been necessary to maintain an inventory of stakes with fingers at different distances from the top end of the stake, so that a screed of the desired vertical dimensions may be secured to the stake. The maintenance of this inventory of stakes is costly, not only in the initial cost of procuring the stakes, but in the manpower necessary to maintain their separation and in the storage space needed in the transportation to and storage thereof at the construction site. The need for a "universal" stake which may be used with screeds with differing vertical dimensions has been long recognized.
Known attempts to provide a stake for use with more than one dimension of screed have included the location of a single finger on opposite sides of the central reinforcing bead in the stake at two different vertical heights. Such single finger stakes have the disadvantage in that the holding capabilities of the single finger are limited and in addition may permit an undesirable rotation between the screed and stake. In addition, two different stakes with the four standard concrete slab depths are generally required.
It has also been known to utilize the screed receiving fingers in pairs at a given vertical distance from the top edge thereof. However, the use of pairs of fingers at multiple depths has presented two problems, i.e., (1) the stake has been impermissibly weakened by the cutting of the metal to form the multiple fingers and (2) the location of the fingers for dimensions of screed other than the one in actual use has interfered with the securing of the screed to the stake.
More recently, applicants have devised a "universal" stake provided with three pairs of fingers, with one of the pairs of fingers serving to receive the bottom edge of two different widths of screed. In this system where two different widths of screed use a common pair of fingers, the top of the stake is received in the downwardly opening pocket of one of the two screeds, and the top of the stake passes through a slot in the screed channel when in use with the other dimension of screed. This system is described and claimed in applicant's pending application Ser. No. 376,608, filed May 10, 1982, now U.S. Pat. No. 4,428,556, dated Jan. 31, 1984, and assigned to the assignee of the present invention.
It is a primary object of the present invention to obviate the deficiencies of known systems and to provide a novel system having a single novel "universal" stake usable with each of four novel screeds of standard widths, as well as a novel method of securing the screed to the stakes.
The advantages of the present system will be readily apparent to one skilled in the art from the claims and from the following detailed description when read in conjunction with the accompanying drawings.